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Posted on 14 October 2011 by dana1981

We recently discussed Santer et al. (2011), which compared the observed trends in the temperature of the lower troposphere (TLT) with those predicted by climate models. The paper also examined claims by John Christy in testimony to US Congress that TLT is warming at just one-third the rate predicted by climate models, and found that he had greatly exaggerated the model-data discrepancy.

Santer et al. also examined what models have to say about short-term trends, and concluded as follows:

"Because of the pronounced effect of interannual noise on decadal trends, a multi-model ensemble of anthropogenically-forced simulations displays many 10-year periods with little warming. A single decade of observational TLT data is therefore inadequate for identifying a slowly evolving anthropogenic warming signal. Our results show that temperature records of at least 17 years in length are required for identifying human effects on global-mean tropospheric temperature."

So there are two key findings here. Firstly, even with man-made global warming taken into account, because of the short-term noise due to the internal variability in the climate system, climate models predict that there will be decades where natural cycles dampen the man-made warming trend.

Pielke's Criticism

"I agree with Santer et al that “[m]inimal warming over a single decade does not disprove the existence of a slowly-evolving anthropogenic warming signal.”

Unfortunately, Dr. Pielke seems to have neglected the second key finding above, as he proceeds to examine 13 years of TLT data.

"they did not recognize that the global average temperature trend in the lower troposphere has been nearly flat as shown, for example, in the figure below from the RSS MSU data...There has been NO long-term trend since the large El Nino in 1998. That’s 13 years."

So why examine 13 years' worth of data? That seems like a rather arbitrary figure - it's larger than 10, but smaller than the 17 year timeframe which Santer et al. concluded is necessary to evaluate the human influence on global temperatures. Dr. Pielke recently answered this question:

"I did not start in 1998 because it was the warmest in the record. I started after that when the MSU LT became ~flat."

However, part of the reason the TLT data is "~flat" over that period is that 1998 was an anomalously hot year. As Dr. Pielke notes in the quote above, 1998 was a "large El Niño year." In fact, not just a large El Niño; 1997-1998 saw one of the strongest El Niños on record. And the TLT data are more sensitive to ENSO events than surface temperature data (Figure 1).

In short, 1998 was an anomalously warm year due to the record strong El Niño that year, especially in the satellite TLT data. Therefore, choosing 1998 as the starting year will result in minimizing the short-term temperature trend.

To further illustrate the point, if we choose a timeframe of 14 years of RSS TLT data, there is a positive trend. If we choose 12 years, it's even more positive. Dr. Pielke has said he chose the RSS data in his critique because it's "the same data that is used in the Santer et al study." However, Santer et al. examined both UAH and RSS data.

If we examine UAH data (which Dr. Pielke has said this is an "outstanding" data set) starting in 1998, even the 13-year TLT trend is positive. The start data also makes a big difference in the short-term trend. The UAH trend is 0.10°C per decade since 1997, 0.06°C per decade since 1998, and 0.18°C per decade since 1999. Note that changing the starting date by a single year from 1998 to 1999 triples the UAH TLT trend.

"My view, is that focusing on a linear trend with respect to a actual nonlinear signal is a substantial oversimplication of how we should expect the climate sytstem to behave both naturally, and in response to the diversity of human climate forcings."

However, over such a short timescale, the forcings are not significantly non-linear, and thus calculating the linear trend is appropriate. In fact, it's an approach that Dr. Pielke himself frequently implements (i.e. here and here and here and here). When asked for evidence that the short-term forcing is significantly non-linear, Dr. Pielke responded that a linear trend does not explain all of the "ups and downs" in the data. However, the ups and downs in the short-term are due to natural variability, and are the reason why Santer et al. concluded that we must examine at least 17 years worth of data to identify the human signal. While the longer-term trend might not accurately be evaluated with a linear fit, in the short-term, it's a reasonable approximation.

Selective Vision

The animation below illustrates the problem with focusing on such short timespans. The first frame shows the data Dr. Pielke has focused on - RSS data since 1998 (plus the linear trend) in blue. The following frame shows what the data looks like if we instead choose UAH data since 1999 (in green). Note that we are not advocating this choice, but simply showing what a large difference such a small change in start date can make. The third frame shows the entire UAH and RSS record.

Even Shorter Timeframes

"The lower tropospheric global annual average temperature trend (TLT) from 2002 until now cannot distinguished from a zero trend."

...and the trends during this time period are different than the trends earlier in the time period. "

However, as Dikran noted in response, it's entirely possible that over such a short timeframe, short-term noise such as ENSO and solar cycles may have masked the continuing long-term global warming trend. Thus testing whether the trend since 2002 can be distinguished from zero:

"is not a particularly interesting hypothesis for the simple reason that the statistical power of the test is very low because the timespan over which the trend is computed is too short."

The signal-to-noise ratio is even less from 2002 to Present than 1998 to Present. Dr. Pielke is moving in the wrong direction, examining less data rather than more.

There are going to be short-term periods in which the noise dampens the underlying long-term signal, and periods when the noise amplifies it. If we're going to examine such short periods of data, we at least must filter out the effects which cause short-term noise.

Removing Exogeneous Factors

Tamino has attempted this analysis by removing a number of exogeneous factors (ENSO, volanic, solar). He found that the long-term warming trend continues in both UAH and RSS, which have been temporarily dampened by those short-term effects over the past ~decade (Figure 4).

Summary

In his blog post, both the data set and start date Dr. Pielke chose minimized the short-term TLT trend. Pielke was well aware of the strong El Niño in 1998, noting it in his post, and yet he chose this year as the start date of his analysis anyway.

It's also unclear why Dr. Pielke chose to make this 'no trend in 13 years' argument in a post commenting on Santer et al. (2011) to begin with, since the paper demonstrates that at least 17 years of data are necessary to evaluate the human influence on the TLT trend. Dr. Pielke also didn't examine why the short-term TLT trend has slowed over the past decade, as was done in Kaufmann (2011), for example.

The main take-home point here is that analysing short periods of data is fraught with challenges due to the short-term noise. It's entirely expected that over periods on the order of a decade, there will be times of little warming in surface temperatures, as Santer et al. (2011) demonstrated. We are currently in the midst of one of those periods. Over the past decade, solar activity has been low, anthropogenic aerosol emissions have risen, and ENSO has been primarily in its negative phase. Thus it's not unexpected that surface temperature warming has slowed, and when we account for these factors, we see that the underlying long-term warming trend continues. As tamino noted when analysing all the main surface temperature and TLT data sets (emphasis added):

"None of the [most recent] 10-year trends is “statistically significant” but that’s only because the uncertainties are so large — 10 years isn’t long enough to determine the warming trend with sufficient precision. Note that for each data set, the full-sample (about 30 years) trend is within the confidence interval of the 10-year trend — so there’s no evidence, from any of the data sets, that the trend over the last decade is different from the modern global warming trend."

Comments

As part of a science project, a 5th grader plots the temperature for the Spring. April 2 has a record high in Boston--95 degrees Fahrenheit. The next seven days show an unusually low average of 60 degrees Fahrenheit. Clearly, based on this trend, Boston is not warming up that year, and spring is not coming.

A baseball player starts off the season batting a poor 200. During the playoffs, however, he catches fire, batting over 400 for 15 games. The last game shows no exception: he starts off with a triple, then hits a home run. However, at his next two at bats, he strikes out and then grounds out. A commentator states that based on the last two at bats, the player is not improving at all, since his batting average is 0 percent.

As silly as both arguments are, I don't see them as substantially different than arguing there has been no warming trend since 13 years ago. Some aspects in climate science are very complex and hard to understand (such as the heat transfer in oceans, or the feedback in clouds); accurately identifying trend lines is not one of these areas.

"Policymakers, in my view, are being misled into believing that the climate should more-or-less monotonically warm when in reality both natural variability and the diversity of human climate forcings makes the issue of climate system heat content much more complex."

With all respect to Dr. Pielke, that is his opinion, but the facts show that he has it backwards. He is also making an unsubstantiated assertion with regards to policy makers being "mislead". Dr. Mojib Latif and other IPCC scientists are aware that the warming will not be monotonic and have in fact cautioned that it will not be, it is actually the "skeptics" who seem to think so.

I say that because it is in fact those who deny the theory of AGW and "skeptics" (even some "skeptic" scientists who know, or should know, better) who get excited every time there is a short-term slowdown or cooling (perceived or real). It is for that very reason that science sites like SkepticalScience (and OpenMind) have had to spend a lot of time refuting claims that global warming stopped in 1998 and 2002 etc. (the number of choices to cherry pick increases as the window is shortened). See here, here, here, and here. There are more, but I think you get the point. The scientific literature abounds with papers speaking to the variability of global temperatures and SSTs (some examples here and here).

Unfortunately, because the global temperature records are inherently noisy (because if internal climate variability, such as El Nino and La Nina), "skeptics" can continue playing this deceptive game (and it is a game for some) of cherry picking statistically insignificant short-term "cooling" trends all the while the statistically significant long-term trend is UP. To do so is in fact misleading policy makers and confusing the public.

Yes, there are short periods where temperatures flatten. But these are present throughout the satellite temperature record. It would be nonsensical to draw any conclusion from these arbitrarily chosen lulls, because the trend continues to be up.

BTW, here is 2006-present:

So if one wants to take some meaning from short periods, one must also conclude that the most recent period indicates warming has not stopped.

The 'pick an arbitrary short period' game can be extended. Look at the following graph of UAH data. Shown are the long-term trend, plus four arbitrarily-chosen non-overlapping but contiguous subdivisions of the whole dataset. (I saw a great graph of this done for the entire GISS dataset once.)

All the short trends are negative, yet how is it that the long-term trend is still rising?

I note once more that we are above the long-term trend for UAH at present, and close to it on other measures. Why would we think global warming has stopped?

DK @6,
It's obvious by just looking at the couple of graphs above that nul hipothesis to Pielke's conclusion passes easily here. Santer et al. (2011) have proved it; no need to repeat.

Certainly, dr. Pielke seems to disregard statistical methods while formulating his conclusions. Further, by cherry-picking the weather data that is likely to support skeptic opinion and ignoring the other aspects of the warming globe, (i.e. ocean heat, discussed here); he shows a biased attitude.

We know many examples of such cherry-picking by many "skeptics". The most prominent one being Chris Monckton, who not so long ago (as lately as April 2011 in Australia) boasted that "Arctic is steadily gaining ice" showning the ice extent data for years 2007-2009 as the "proof". We all know now that Monckton was not only cherry-picker but a [-snipped-] because he didn't even show the 2010 data (available to him at the time) as that data would disprove his claim. Now, when the 2011 ice data equalled the record low of 2007, no one listens to Monckton's [-snipped-] anymore.

It's easy to rebut Monckton (his arrogance also works against him), Pielke is more subtle but still uses the same cherry-picking methods.

Firstly, thanks for a well-written and informative post. Would it be possible to add uncertainties to the measured trends (e.g. 0.18C since 1999)? Presumably they are quite large for such short time-periods, and this would help emphasise how they are not particularly useful. Significance tests would serve the same purpose.

I'm also interested in what sort of studies have been done regarding the linearity/non-linearity of various aspects of the climate system. Any references would be greatly appreciated - sorry if this request is too vague.

dana1981 - In your analysis you miss, in my view, a fundamental issue. Jim Hansen has written

"The Willis et al. measured heat storage of 0.62 W/m2 refers to the decadal mean for the upper 750 m of the ocean. Our simulated 1993-2003 heat storage rate was 0.6 W/m2 in the upper 750 m of the ocean. The decadal mean planetary energy imbalance, 0.75 W/m2, includes heat
storage in the deeper ocean and energy used to melt ice and warm the air and land. 0.85 W/m2 is the imbalance at the end of the decade.

Certainly the energy imbalance is less in earlier years, even negative, especially in years following large volcanic eruptions. Our analysis focused on the past decade because: (1) this is the period when it was predicted that, in the absence of a large volcanic eruption, the increasing greenhouse effect would cause the planetary energy imbalance and ocean heat storage to rise above the level of natural variability (Hansen et al., 1997), and (2) improved ocean temperature measurements and precise satellite altimetry yield an uncertainty in the ocean heat storage, ~15% of the observed value, smaller than that of earlier times when unsampled regions of the ocean created larger uncertainty." [http://pielkeclimatesci.files.wordpress.com/2009/09/1116592hansen.pdf]

A rate of heating of 0.85 Watts per meter squared corresponds to 1.38 x 10^22 Joules per year. This a metric than can be evaluated on a yearly basis (with uncertainties) and tracked with time. Since 2002, as shown in the lower tropospheric plot and in the upper ocean data, little of that heat has accumulated there. There is not enough melt of sea ice or glaciers to account for it there. "Global warming" has nearly stopped using these two metrics, irrepsective of the long term trend and whether it is due to natural variations or an incomplete understanding of human climate forcings.

The only remaining two options are the deep ocean and/or out into space. We should be focusing on this issue instead of how long a data set is needed to ferret out a slow linear trend.

One other comment; you report

"Tamino has also previously performed a multiple regression of temperature on various short-term effects, including the Multivariate ENSO Index (MEI), and confirms that TLT data are much more sensitive to ENSO than surface temperature data".

However, as reported in CCSP 1.1, the surface and lower tropospheric temperature trends are supposed to be closely linked in terms of trends. [ http://www.climatescience.gov/Library/sap/sap1-1/finalreport/default.htm].

What one sees in the defense of SkS of the long term linear trend is an effort to explain away differences that occur whenever they (unexpectedly) appear. This may provide encouragement for the convinced but, I suspect, is making a large number of others (e.g. including policymakers) suspicious of the claims. Examples of the unanticipated (as illustrated by Jim Hansen's statement) include reported deep ocean heating as a source of the "missing heat", the disparity between trends in the lower troposphere and the oceans, and need to adjust the data to account for ENSO, etc.

And yes, the absence of much of a trend since 2002 fits into the conclusion that the linear trend oversimplifies the actual behavior of the climate system.

My recommendation is, that instead of spending the effort to show that 2002 to 2011 (or 1999 to 2011) is too short of a time to necessarily see the linear trned, if it is there, that you focus on reporting on the observed data without a pre-chosen view that you are trying to defend.

It amazes me that with the diversity of human climate forcings, the newly recognized higher importance of solar forcing, of internal variations and other effects, that you persist in assuming that the slow forcing of added CO2 will dominate if we integrate over enough years. Perhaps you are right, but you will not be convincing unless, in my view, you adopt a different tact.

That tact, I suggest, is to focus that too large of an increase of the atmospheric concentration of CO2 as unknown as we do not know its consequences in terms of biogeochemistry. A prudent behavoir would be to encourage limiting how much we put into the atmosphere. As an associated effect, its positive radiative forcing would be less.

One way to look at the temperature record is to look at how adding the years after 1998 affects the long term linear trends. I made a graph from WoodForTrees of the 4 main data sets, starting in 1979 (so I could use the entire satellite record), and comparing the trends from 1979 thru the end of 1998 with 1979 thru the present (I made the graph about a month ago so it isn't updated for the most recent months). For GISS and UAH, the trend actually got a little larger when the last 13 years are added; the trend just barely decreased for RSS and HadCrut. Overall it doesn't look like adding the "flat" years made much of an impact on the long term trend, which you would think would be the case if the warming ended in 1998.

pielkesr#10: "one sees in the defense of SkS of the long term linear trend is an effort to explain away differences that occur whenever they (unexpectedly) appear. "

This philosophical argument cuts both ways. As warming continues, those who say 'warming stopped in ___ ' are also left to explain those differences. Where are those explanations in more depth than 'its a natural cycle'?

"instead of spending the effort to show that 2002 to 2011 (or 1999 to 2011) is too short of a time to necessarily see the linear trned, if it is there, that you focus on reporting on the observed data without a pre-chosen view"

Again, a question that must be asked on both sides. How is using the entire satellite dataset a pre-chosen view? How is choosing an arbitrary short time period not a pre-chosen view?

What I find missing here is internal logical consistency. If trends from 5 year periods are considered significant, then any 5 year period is as good as any other -- and that must include the most recent.

As far as effort is concerned, it is far more effort to explain these short period variations than to address the significance of the long term trend.

Muoncounter, you ask: "Where are those explanations in more depth than 'it's a natural cycle'?"

There are two effects from natural cycles. First is ocean-atmosphere exchange, second is radiative balance changes from volcanoes, ENSO-induced clouds, etc. The most in-depth explanation would consider both simultaneously and show heat accumulating at varying rates. The rate, generally speaking, was higher in the 80's and 90's and lower but still positive in the past decade.

I do not understand why you write with regard to Dana's piece that "It amazes me that with the diversity of human climate forcings, the newly recognized higher importance of solar forcing, of internal variations and other effects, that you persist in assuming that the slow forcing of added CO2 will dominate if we integrate over enough years. Perhaps you are right, but you will not be convincing unless, in my view, you adopt a different tact."

Dana's key opening point was that skeptics are and have been using short runs of temperature data to claim that global warming has stopped or reversed. This point was illustrated by Dana and others who posted graphs illustrating just how easy it is to select a short run of years and show that for those short stretches of time the trend is negative, while over a slightly longer time frame the trend is positive.

As brief trends are often reversed in the wider trend once a statistically suitable longer span of years is considered (17 years, according to Santer et al (2011), being the minimum required for statistical significance), and once we look at such a span of recent years the global temperature is seen to be rising, it seems to me your attempt to argue that short term trends are of more interest than the overall longer-term trend is flawed.

Incidentally, the word you should have used in calling for Dana to change his course of inquiry is "tack" and not "tact": "tack" is a nautical term which has to do with a vessel's course or direction of movement and is of particular importance to sailing ships. A sailing ship crossing the Atlantic, for example, might tack many dozens of times in order to maximize its use of wind energy or to avoid storms and areas of calm winds. When plotted on a map, individual tacks (the term can describe the run of the ship along a particular short-term course) may well make it appear that a ship heading from Liverpool to New York is heading for either Greenland or South America or even at times back toward Europe, but extended over time the various tacks produce a directional trend that causes the ship to arrive at its intended destination.

Metaphorically, it seems to me that you are trying to argue that an individual "tack" takes precedence over the overall course and that we do not know which overall course the global temperature is on.

#5 Skywatcher, selecting the years on shorter period trendlines so they begin when the solar cycle is rising to the max about 1/3 from the top (2-3 years before the actual maximum (sunspots)). Can't find the image now (possibly lost somewhere in Tamino archives), but that was the idea, to tease out the maximum effect of the sun in current conditions of GHGs. Needless to say, selecting the years the opposite way gives increasingly steepening trendlines.

In terms of how we separately view the global warming issue, we clearly differ in a fundamental perspective. I have concluded that the appropriate way to monitor multi-year (multi-decadal) global annual-average warming (or cooling) is in terms of heat accumulation in Joules, which is by far dominated by the oceans. Even Jim Hansen has agreed with this view.

Here is one example of its value. If, for example, a large volcanic eruption caused a large loss of Joules, the global warming "clock" would be reset.

In contrast, the use of a linear trend would see this cooling as a short term blip and the positive linear trend would be retained until (and unless) the cooler heat content persisted long enough.

I have used the muted (lack) heating in the troposphere since 2002 to reinforce that we need to focus on the ocean.

I agree with almost all of your comments about the issue with the use of short term trends. While it shows that lower tropospheric warming has essetially halted in the last few years (which we seem to agree on), it tells us nothing about the future, nor the reasons for the lack of warming.

However, by not focusing on the ocean heat content issues, including the reported heating in the deeper ocean including how it got there, you are missing an opportunity to reach out to those you call (perjoratively in my view although some like this label) "climate skeptics".

Lets agree that it is a short term flattening in the lower tropospheric temperatures (since 2002) that we will all follow to see if it persists in the coming months and years. This short term trend does not tell us that the long term trend has been significantly changed (yet).

Lets also agree, however, to focus on the actual best measure of global warming - the oceans.

Muoncounter, the real sidetrack is OHC. But regardless the unshakeable trend is 0.4 over 30 years (UAH). There's also a somewhat shakeable change in trend from 80's and 90's to the 00's although it's still clearly up. I would also note that 35 years places the starting point into the cooler 70's.

Prof. Pielke wrote "I agree with almost all of your comments about the issue with the use of short term trends. While it shows that lower tropospheric warming has essetially halted in the last few years (which we seem to agree on)"

No, it shows nothing of the sort. The failure to reject the null hypothesis (flat trend) does not imply that the trend actually is flat, that is a classic misinterpretation of a statistical hypothesis test.

If the the null hypothesis is not rejected, there are essentially two reasons why this can happen. The first is that the null hypothesis is correct. The second is that the period over which the trend is calculated is too short to reliably estimate a trend of the expected magnitude. To rule out the second possibility, you need to show that the test has sufficient statistical power to reliably reject the null hypothesis if it is false. You have yet to demonstrate this, and so you should not be claiming that "lower tropospheric warming has essetially halted in the last few years".

"Since 2002, as shown in the lower tropospheric plot and in the upper ocean data, little of that heat has accumulated there. There is not enough melt of sea ice or glaciers to account for it there. "Global warming" has nearly stopped using these two metrics, irrepsective of the long term trend and whether it is due to natural variations or an incomplete understanding of human climate forcings."

However, we all agree that global warming is not measured only by TLT and upper ocean data.

"What one sees in the defense of SkS of the long term linear trend is an effort to explain away differences that occur whenever they (unexpectedly) appear. This may provide encouragement for the convinced but, I suspect, is making a large number of others (e.g. including policymakers) suspicious of the claims."

A main point of Santer et al. is that these short-term deviations from the long-term trend are not unexpected, and thus I strongly disgree with your characterization of our post.

What I think makes policymakers suspicious are arguments like yours, when they are told that the lower atmosphere hasn't warmed since 1998 or 2002.

"My recommendation is, that instead of spending the effort to show that 2002 to 2011 (or 1999 to 2011) is too short of a time to necessarily see the linear trned, if it is there, that you focus on reporting on the observed data without a pre-chosen view that you are trying to defend."

Our "pre-chosen view" is simply that we must examine all available climate data, and not selectively omit certain pieces of it (like TLT temperatures prior to 2002 or 1998, or the entire UAH record, for example).

"I agree with almost all of your comments about the issue with the use of short term trends. While it shows that lower tropospheric warming has essetially halted in the last few years (which we seem to agree on), it tells us nothing about the future, nor the reasons for the lack of warming. "

I would agree that the trend in the short-term, very noisy TLT data has slowed the past few years (though Dikran, who has much more statistics expertise than me, might smack me for saying so), but this is not an unexpected result (and I would go so far as to call it an expected result, given changes in ENSO, aerosols, and solar activity over that period), and certainly agree this tells us nothing about the future.

"Lets also agree, however, to focus on the actual best measure of global warming - the oceans."

On this we don't agree, and I think your pursuit of this goal is doing much more harm than good.

In order to convince others that we should focus on OHC, you have also made this argument that TLT has not increased since 1998 or 2002. There are a lot of people who are looking for excuses not to take action on climate change, and they will gladly latch onto your "no warming since 1998" argument whilst ignoring your "we should focus on OHC" argument (Anthony Watts being one of them). Your strategy here gives the delayers the ammunition they need.

As we have said many many times, OHC is a very important metric, but there should not be a single metric. We should examine all metrics, including OHC, TLT, surface temps, ice mass, etc. And as noted above, my main concern is providing ammunition for those who seek to undermine any and all action to address climate change, which is what your argument here does. I suggest you re-evaluate your messaging strategy, because it is currently doing more harm than good.

Dikran Marsupial - Regarding #21, we will just have to disagree and move on. You are asking if the recent data alters a longer term trend significantly. I ageee; it does not. But what I am asking is if you took the data since 2002, does it show a trend that is significantly different than zero.

To say the tropospheric heating has not been less in recent years, is like saying a car is still accelerating with the speedometer says it is at a nearly constant speed over the last few kilometers.

Dr. Pielke, I'm reading your comments on Santer et al. and here to the best of my abilities but I haven't yet seen an explanation for your use of short time scales in response to a paper that was explicit in calling this approach wrong-headed for easily understood statistical reasons. If using >17 years is insufficient to draw conclusions about the agreement between models and observations, why do you think it's appropriate to do exactly that?

I also don't see an explanation for your use of RSS over UAH data when Santer et al. used both (RSS happens to give a flat slope for the same time period that UAH gives a positive one), and your explanation of picking 1998 as the starting point in a type of analysis which is well known to be sensitive to end-point selection is also unsatisfactory, especially in light of the short-term variability creating noise that makes it difficult to tease out all but the strongest trends into statistical significance. Yes, 1998 as a start makes a "flat" trend, but any year prior and several years after 1998 produce a positive trend. Could it be that this apparently flat trend is entirely a relic of 1998's status as an unusually warm year, and therefore an illusory trend that's not worth bothering with?

To me, these are the main points of contention here and you are apparently not addressing them. It's especially disheartening because these exact same methods (selective use of end points, short time scales, and focusing only on data that produce low or no trends) have been abused extensively by people who argue that there's no anthropogenic warming, something I know you disagree with.

"There are a lot of people who are looking for excuses not to take action on climate change, and they will gladly latch onto your "no warming since 1998" argument whilst ignoring your "we should focus on OHC" argument (Anthony Watts being one of them). Your strategy here gives the delayers the ammunition they need."

Unfortunately, what you assume is a perspective of "climate change" that is a much narrower view than I and many of my colleagues have concluded. Moreover, you focus on "climate change" when the focus should be on "climate", including risks we face if past extreme events reoccur but with today's societal exposure. We discuss this approach in our paper

Anthony Watts, and others, do not conclude there is no human role in the climate system, nor that we should not do things that are environmentally positive. You misstate this information.

The disagreement, and I share this, is that the focus almost exclusively on added CO2 by itself, could prevent other important issues from being addressed. It also makes geoengineering, such as the dangerour idea of ejecting aerosols into the stratosphere, a proposed approach to mitigate the radiative effect of added CO2. This why the failure to accept a slowing down of the tropospheric warming, which seems so obvious to me, actually prevents a more constructive discussion with the so-called "skeptics".

I suggest you, and others, hurt the environmental movement by focusing so heavily on just one environmental issue.

Instead of selecting an arbitrary timeframe, which lends itself to statistical errors, why not examine the moving average. This eliminates the subjective error in the analysis.

Using HadCRU monthly values (other datasets produce similar numbers), the 120-month moving average was generally increasing over the following timeframes: 1896-1903, 1914-1946,1957-1967, and 1979-2008. During the other timeframes it was decreasing: 1887-1896, 1903-1914, 1946-1957, 1967-1979, and 2008-present.

Since the moving average had been increasing since 1979, it is not surprising than any start date chosen for analysis since then would show a positive slope. The moving average has only been decreasing for three years, so only a short timeframe would show a temperature decrease.

With all respect, you are going off topic and obfuscating. Normally off topic posts are deleted. This thread was written to address the choice (by you) of 1998 as a start date with which to calculate a short-term trend and then confidently assigning importance to the resulting trend. You now seem to have shifted your focus to 2002, but this all started with the curious choice of 1998. Trying to shift focus to 2002 looks to me like implicit acceptance by you that 1998 was not an appropriate start date for calculating a short-term trend.

We have discussed OHC with you before, and readers will recall we agree with you and Hansen that OHC is an important metric (one of several), we have been very clear on this, so please don't try and suggest otherwise. SkepticalScience has numerous threads that speak to OHC and energy in the climate system. See here and here. But that is not what is at issue on this thread, so if you wish to discuss OHC please do so on the relevant thread or at our ongoing discussion about OHC here. Thank you.

And Dikran's questions (and points) are actually very relevant to the topic of this thread and their implications are important, so I for one encourage you to look at the statistical power of your hypothesis tests for the stated time frames and to please let us know what you find. Thanks.

Prof. Pielke wrote: "Regarding #21, we will just have to disagree and move on."

No, I'm sorry Prof. Pielke but you cannot simply ignore correct statistical practice, it is a cornerstone of modern scientific method. If you cannnot demonstrate that an hypothesis is supported by the data then you should not use it as a basis for your arguments. If you continue to make such arguments there is a strong possibility that you will be misleading those who are listening to them.

"You are asking if the recent data alters a longer term trend significantly. I ageee; it does not."

So you would agree that your third hypothesis is not supported by the data then? If so, that is good, but one wonders in that case why you put the hypothesis forward?

"But what I am asking is if you took the data since 2002, does it show a trend that is significantly different than zero."

I have already said (here) that I agree that your first hypothesis is undoubtedly correct. However I have also pointed out at least three times that unless the hypothesis test has useful statistical power the fact that the trend is not significantly different from zero is essentially meaningless. You have made no attempt to address that issue whatsoever.

Now I have asked you three times to state the statistical power of the test and have not recieved a direct answer on any of these occasions. This is not unreasonable question to ask a senior academic in a field that deals with the analysis of observational data, the proper interpretation of a statistical hypothesis test is something that every scientist should feel comfortable with. There is no point in asking again, so I won't, but will instead have to conclude that you are either unable or unwilling to answer the question. I find that rather troubling.

Jonathon, unfortunately there is no "the" moving average. You must choose the timeframe for it--the surrounding two data years, or the surrounding four years, or....

And you're not examining just the moving average at a point, but the trend in the moving average over some number of years. How many years should you use? 2002 until now? 2008 until now? 1979 until now?

How do you judge whether that trend is representative of the underlying population's trend (the "real" trend, in some sense)? You've got to apply a statistical test of some sort, but choosing that test requires attending to Dikran's explanations and cautions.

Computing moving averages is one way to smooth out the noise so you can see the signal, but it is not magic. There still is noise, so you still need to examine the trend over a long enough time to have the statistical power to detect the signal over that noise.

You say:"While it shows that lower tropospheric warming has essetially halted in the last few years (which we seem to agree on), it tells us nothing about the future, nor the reasons for the lack of warming"

And "This short term trend does not tell us that the long term trend has been significantly changed (yet)."

I do not wish to be pedantic, but this is not what you told readers on your blog. You said:"they did not recognize that the global average temperature trend in the lower troposphere has been nearly flat as shown, for example, in the figure below from the RSS MSU data...There has been NO long-term trend since the large El Nino in 1998. That’s 13 years."

You were quite assertive that this was a noteworthy finding and went so far to underline the '13 years'.

And as for your claim "lower tropospheric warming has essentially halted in the last few years". "Halted" is very definitive, and is not consistent with your observation that "This short term trend does not tell us that the long term trend has been significantly changed (yet)".

The fact remains that trends for 2002-present is simply too short a period to draw any meaningful conclusions, especially if one does not consider all the data and the role of aerosol loading, solar minimum, ENSO etc. It is also not an accurate characterization of what is happening. A more accurate way of describing it would be a temporary slow down, because we know from observations (e.g., Hansen et al. 2011) that the climate system is still in a positive energy imbalance and has continued to accumulate energy since 2002, albeit at a slower rate.

Earlier@10 you also made the claim that:"What one sees in the defense of SkS of the long term linear trend is an effort to explain away differences that occur whenever they (unexpectedly) appear."

and

"The only remaining two options are the deep ocean and/or out into space. We should be focusing on this issue instead of how long a data set is needed to ferret out a slow linear trend."

I take strong exception to those characterizations. It is the 'skeptics' who are trying to explain away AGW by focusing on the noise in the system and ferreting out out windows of time when there was little or no warming. Also, applying statistical analysis correctly as we are doing here is not "defending" anything except the intergity of the scientific method and appropriate statistical analysis. That is something that I would have hoped that you would endorse.

To suggest that we, or IPCC scientists, are trying to "explain away differences" is simply not true. A great amount of time is spent by climate scientists looking at climate variability and working towards improving our understanding the climate system, I provided but a few links to the literature in my previous post @2. As I mentioned earlier, it is 'skeptics' who are trying to hide the incline and disappear the warming. I find it very odd that "skeptic" scientists do not use short-term trends to highlight periods of more rapid warming, why are such periods of warming any less important or of less scientific interest than hiatus periods? That they don't just highlights their confirmation bias.

Doing that is very harmful because if fabricates debate, fosters doubt and misleads people into a false sense of security that the warming is not as bad as expected-- all based on statistically meaningless trends.

As for your characterization of the "slow long term" trend is inaccurate in my opinion. That is a subjective and relative term and what people should correctly understand by 'slow' very much depends on the context. We are currently warming much faster than during the PETM, for example.

Dikrans point at (21) about the null hypothesis test has been unanswered. Dr. Pielke, Sr. (24) has requested a significance test when he and everyone else has agreed that it would have no meaning. What is the point of that?

OHC versus TLT and police making: Granted, OHC is a stronger metric than surface temps, but we have very scant information on OHC and multitudinous and long records of surface temps. Why would anyone advocate ignoring the bulk of the information available when making policy?

Focusing on OHC only plays into the hands of those that profit from policies which do not change BAU, because there is not yet a great deal of information about OHC.

Re: "I suggest you, and others, hurt the environmental movement by focusing so heavily on just one environmental issue. "

Whenever you have multiple problems and limited resources, you have to focus primarily on getting the best return on your investment. The vast majority of climate researchers are convinced that reductions of CO2 production improves our future situation more than any other factor. Maybe that is where we have recognise that there is disagreement between Dr Pielke, Sr. and a handful of others, and the majority, and move on.

Dr. Pielke, you wrote, speaking of 2002 to present:
"While it shows that lower tropospheric warming has essetially halted in the last few years (which we seem to agree on), it tells us nothing about the future, nor the reasons for the lack of warming."

Will you agree to the statement that, while not telling us anything about the future, or the long term trend, that clearly lower tropospheric warming has essentially resumed at a similar or slightly faster pace than the long term trend from 2006 to now?

I mentioned that it was a 120-month (10-year) moving average, and is centered around the dates mentioned. The nice thing about employing a moving average, is that one does not need to choose the timing. This shown in the earlier posts depending on the starting year for computing trends.

If you object to using the change in the moving average, then the maximum value occurred in July, 2002 (a local maxima occurred in July, 2005, but it did not exceed the earlier maxima). Hence, any trend starting in 2002 is likely to show a temperature decline. In fact, any trendline starting after Jan, 1997 (with the exception of the La Nina '99) shows a slightly negative trend (although not significantly different from zero).

Wow, Dr.Pielke, if you'll bear with a novice here and forget my last two posts.

Would you agree to the statement that "While it tells us nothing about the future, nor the reasons for increased warming, that from 2006 to now lower tropospheric warming has essentially resumed, at what appears to be a much faster pace than the 30 year trend?

Jonathon, you missed my points. Your choice of 120 months for your moving average is an example of the very same arbitrary choice of timing you claimed to have avoided by using a moving average. Why did you choose 120 months (10 years)? Why not 132 (11 years), which might better take out the solar cycle? Why not some other?

You have not avoided arbitrary choice of starting years for computing the trends. You must choose the starting and ending years (and therefore all the years in between) across which you compute the trend in moving average. You did exactly that. Why did you choose those particular starting and ending years? Why not some others?

Your "solution" of simply using moving averages isn't a solution to the issue you claimed it is.

I originally used 5 years as reported on many sites, but it did not filter out all the noise, particularly solar cycles and ENSO events. Although 5 years is a better choice for looking at how these events affect temperature. Using 11 (or 9) years does not change the results.

At some point, all statistics are arbitrary, because we have chosen them for use. I never said this was a "solution," just better than arbitrarily selected a start date for linear regression.

Well - its time to move to another topic. To argue over whether the warming in the lower troposphere started in 1998 or in 2002 misses the point. All one has to do is look at figure 7 TLT in http://www.ssmi.com/msu/msu_data_description.html.

Figure 8 clearly shows the step change after 1998 along with the large warming at higher northern latitudes.

You do not need statistics to see the obvious. We all agree the lower troposphere is warmer today than it was in 1979.

Lets move on as the comments are starting to deteroriate as they did when I first started to comment on SkS. You are never going to be successful in building a bridge to those who do not share your viewpoint unless you recognize the value of the other perspectives.

Finally, Chris G, you write

"The vast majority of climate researchers are convinced that reductions of CO2 production improves our future situation more than any other factor."

I am not sure where you obtained this information, but can assure you that this is not case, as exemplified by recent co-authored papers I have been involved with; e.g.

Dr Pielke "To say the tropospheric heating has not been less in recent years, is like saying a car is still accelerating with the speedometer says it is at a nearly constant speed over the last few kilometers."

I think a car analogy can be useful, but not this one.

If you rethink a car being under cruise control, but with the power output being regulated rather than the speed, it's a lot like the climate system being 'driven' by a forcing - in this case CO2 and other GHGs. And we know why cars are not controlled in this way. Because the natural terrain will cause the vehicle to vary its speed.

Speeding up and slowing down in various conditions despite the power generated being exactly the same. And that's what we mean when we talk about the climate system, oceans and all, being forced in one direction. Just as a car with constant power will not show constant speed, it will still get the occupants where they're going - even if the terrain is hilly, or twists a lot, or offers fords with flowing water rather than bridges, or gives a bumpy ride over unmade surfaces.

And GHGs do the same for the climate system. They will get us where they're driving us. We simply don't have a map detailed enough to tell us exactly when the bumpy rides and the variable speeds will occur nor how long they'll affect our progress. We have to map our terrain as we go. We call it natural variability.

Dr. Pielke, how can we ever "move on" if you've never bothered to address what this post has been about? That sounds to me like you're asking us to simply ignore the issues that were raised.
Here's what you have not answered regarding this SKS post:

1) Why did you select a 13 year period in one of two datasets to make the argument that TLT trend has been flat, when the other dataset disagrees AND the time scale you used probably makes your conclusion statistically insignificant?

2) Why won't you do the trivial work of establishing statistical significance for your claims, claims you've used to criticize a published and peer-reviewed paper?

If you can't be bothered to respond to intelligent and careful criticisms of these arguments you're making, it's irresponsible to make them in the first place. This is doubly so since your arguments echo and feed into dishonest tactics used by people who want to avoid dealing with important environmental issues by denying the extent of the problem.

>>You are never going to be successful in building a bridge to those who do not share your viewpoint unless you recognize the value of the other perspectives.

You have repeated this admonition a number of times, and it is not helpful in leading to a better understanding of climate science. In essence, you want us to accept your viewpoints just for the sake of agreement. Truth is not arrived at that way.

I will repeat what a number of posters have asked for here, what I implied in my very first post: what is the statistical significance of your claim? If there is no statistical significance, then you should not mention it, or admit that it was not prudent to do so. Your other arguments about heat in the ocean may or may not be relevant, but they have little to do with you initial statement.

I am also noticing a disturbing pattern from you. You make a controversial claim ("SkS makes ad hominem attacks on Christy," "CO2 forcing is only 28%," "the global average temperature trend in the lower troposphere has been nearly flat"), and then when pressed to substantiate these claims, you claim that the details are not really important to the bigger picture, and we should just move on. If these small details are not important, why raise them to begin with?

I realize this may be off-topic, but I an intensely interested lay person learning as quickly as possible: Muonocounter commented:" The result of that analysis (Tamino's)is the familiar 35 year trend of 0.18 deg C per decade, which seems unshakeable at this point. " My quick calculations of another 85 years to reach 560/CO2 doubling (assuming 2 ppm per year) at 0.18 C per decade yields a total temp increase of approx. 2.3 C for CO2 doubling...why is this below commonly accepted median of 3.0 C for climate sensitivity? Thanks!

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Moderator Response: [Sph] People will gladly answer such questions, but please make some effort to find an appropriate thread using the search box at the top of the page. Many regulars monitor the "Recent Comments" page and so will see and respond to your question where ever you put it.

You can find my response to your question here, where that post will also give you other relevant information.

All - We are going around in cirles on this issue. The parallel to cruise control misses that there are multiple forcings and feedbacks occurring. The "car" is not driving on a simple two dimensional surface. GHG forcing is but oe of a diverse range of human and natural climate forcings.

Nonetheless, while we still disagree on a number of issues, I found many of your comments informative. I plan to summarize my conclusion from these discussions later next week.

Thnak you again for the opportunity to interact (mostly :-) constructively.

With all due respect and thanks to our guest here, Dr. Pielke Sr. for his constructive interactions on this thread, there yet exist a number of issues needing elaboration and elucidation. Such as:

"All one has to do is look at figure [references a statistically insignificant short period of time in the satellite lower troposphere datasets]..."

and

"Figure 8 clearly shows the step change after 1998 [again references a statistically insignificant short period of time in the satellite lower troposphere datasets] along with the large warming at higher northern latitudes.

You do not need statistics to see the obvious."

[Emphasis added]

Again, a repeated demonstration of the power of visual inspection as a metric of statistical significance in the scientific arena; all in lieu of actual analysis of time-series too short by definition of receiving rigorous statistical analysis of their significance (if any).

Given these precedents, let us use our new-found powers of visual inspection to ponder the scientific significance of these:

Please note that all four of these time-series involve trends of decades-to-hundreds-of-millennia (all greater than the 30 years minimum standard to be considered climate).

It is indeed exceedingly clear that one does not need statistics to see the obvious...

Allow me to attempt to summarize the state of the TLT discussion at this point.

1) We agree that over very short timeframes, it's possible to select TLT data for which the trend is small. SkS has said this is actually an expected result (see Santer et al. and the influences of ENSO, solar, and aerosols over the past decade). Dr. Pielke has not explicitly agreed with this point (in fact for some reason he seems to oppose trying to determine why the short-term warming has slowed), but does agree that the short-term slowing of the TLT trend tells us absolutely nothing about global warming.

2) Dr. Pielke says

"the failure to accept a slowing down of the tropospheric warming, which seems so obvious to me, actually prevents a more constructive discussion with the so-called "skeptics"."

I think this is a fundamentally unscientific position from Dr. Pielke. He seems to believe that we should cherrypick short timeframes which are not statistically significant, and should not try to examine what effect various factors like ENSO have had on temperatures over that short, cherrypicked timeframe, in order to create a "more constructive discussion with the so-called skeptics." Frankly I think this is a rather appalling statement and could not disagree more. We should not lower the quality of our scientific and statistical analysis just to make the "skeptics" happy. We have agreed that TLT warming has slowed recently, but

a) the change is not statistically significant and
b) there are reasons behind the change

That Dr. Pielke admonishes us for noting these two facts disturbs me. As I said, he seems to be advocating an unscientific approach just to make "skeptics" happy.

3) Dr. Pielke has agreed with our criticisms regarding cherrypicking of short-term data; however, I still fail to understand why he has engaged in this type of argument if he agrees it is invalid, unless he believes it will somehow bridge the gap between our "side" (that being the side of accurate scientific and statistical analysis) and the side of the "skeptics" (that apparently being the cherrypicking side).

Perhaps not directly on topic, but it does get a mention above. I've noticed at his blog (and now here) that Pielke Snr refers from time to time to his concern about biogeochemistry effects of increased CO2, but I can't say that I have ever noticed a succinct summary on his blog (or elsewhere) as to what specifically he is referring to. Ocean acidification obviously springs to mind, but it always seems his meaning is broader.

I would be more than happy if he could explain here. I would also be curious as to why, if he considers this alone to be reason to take serious action on CO2 emissions, does he spend an enormous amount of time on disputing the way other climate scientists are measuring or understanding global warming, when that is obviously interpreted by the climate change skeptics as meaning there is too much uncertainty to bother starting serious action to reduce CO2.

It always seems to me that only a tiny fraction of his time is devoted to reminding the likes of WUWT readers that he actually thinks CO2 emissions should be reduced. The rest is on criticism which they interpret as meaning there is no need yet for serious action.